This can be used to limit privileges of new accounts.
Accounts created by earlier versions of the software may not have a recorded creation date, and will always be considered to pass the age test.

When left at 0 (the default), all registered accounts will pass.

Some other useful settings:

$wgAutoConfirmAge=600;// ten minutes$wgAutoConfirmAge=3600;// one hour$wgAutoConfirmAge=43200;// half a day$wgAutoConfirmAge=86400;// one day$wgAutoConfirmAge=259200;// three days$wgAutoConfirmAge=86400*3;// three days